A tree harvester head is used to process a tree. The harvester head is normally attached to the end of an arm of a forestry work machine. In operation, the head grips an upright growing tree and fells it. One or more drive wheels of the head feed the felled tree through the head during which one or more delimb knives delimb branches from the tree trunk. If configured to do so, the head may then cut the delimbed tree trunk into pieces or fixed length with a chain saw or other cutting device.
The delimb knives may be located on one or both sides of the drive wheels. For applications involving trees with branches near the tree base, it may be particularly useful to employ a lower delimb knife on the same side of the drive wheels as the butt saw.